Abstract

We have calculated the consensus sequence for human mitochondrial DNA using over 800 available sequences. Analysis of this consensus reveals an unexpected lack of diversity within human mtDNA worldwide. Not only is more than 83% of the mitochondrial genome invariant, but in over 99% of the variable positions, the majority allele was found in at least 90% of the individuals. In the remaining 0.22% of the 16,569 positions, which we conservatively refer to as “ambiguous,” every one could be reliably assigned to either a purine or pyrimidine ancestral state. There was only one position where the most common allele had an allele frequency of less than 50%, but this has been shown to be a mutational hot spot. On average, the individuals in our dataset differed from the Eve consensus by 21.6 nucleotides. Sequences derived from sub-Saharan Africa were considerably more divergent than average. Given the high mutation rate within mitochondria and the large geographic separation among the individuals within our dataset, we did not expect to find the original human mitochondrial sequence to be so well preserved within modern populations. With the exception of a very few ambiguous nucleotides, the consensus sequence clearly represents Eve's mitochondrial DNA sequence.